This research project consists of the study of the response of a solid rhabdomyosarcoma tumor system in rats to high-energy heavy charged-particle beams. The objectives are: (1) to compare tumor responses from irradiation in vivo and in vitro by various charged particle beams in both single and fractionated exposures in order to aid in the selection of the most promising beam (or beams) for clinical application; and (2) to study in depth the heavy-ion radiation response of this tumor via several end points, including TCD50, radiation-induced growth delay, cell survival (in vitro assay) after irradiation in vivo, cell survival of both oxygenated and hypoxic cells, and in addition, several cell-kinetic end points. Also, the combined action of the heavy-ion beams and hypoxic cell sensitizers is being studied.